The present invention relates to a solid state light source lighting device for lighting a solid state light source such as a light-emitting diode (LED), as well as a lighting system using the same.
Japanese Patent Application No. JPA 2005-267999 discloses an LED-type illumination device capable of performing a dimming control for an LED based on a lighting control signal. This device carries out, by determining a dimming ratio based on a lighting control signal, PWM control for controlling lighting of the LED if the dimming ratio is higher (or brighter) than a predetermined value, and peak value control for controlling lighting of the LED if it is lower (or darker) than the predetermined value.
According to the technique of JPA 2005-267999, a dimming ratio is determined based on a lighting control signal and, depending on whether the dimming ratio is higher or lower than a predetermined value, a control is switched between PWM control and peak value control. However, operation becomes unstable before and after switching between PWM control and peak value control, causing flickering.